Lacrimal drainage capacity, age and blink rate

PURPOSE: The aim of this study was to investigate the influence of blink rate on lacrimal drainage capacity in different age groups. METHODS: The drop test for lacrimal drainage capacity was recently described by us. In the drop test, drops of 10 &mgr;l, 15 &mgr;l or 20 &mgr;l of lukewarm saline are repeatedly instilled in the tear film during three minutes. Excessive saline solution is then removed and the volume drained by the lacrimal passages is calculated. The drop test was performed in 40 individuals of two age groups, 10-30 years and 60-80 years. The drop test results were recorded when the subjects tried to blink at frequencies of 90 and 180 blinks/three minutes. RESULTS: The drop test results were significantly higher in the young than in the old subjects. At the lower blink rate, the lacrimal drainage capacity was 363 &mgr;l/3 min. in the young and 155 &mgr;l/3 min. in the old subjects. At the higher blink rate, the lacrimal drainage capacity was 520 and 200 &mgr;l/3 min., respectively. The increases in lacrimal drainage capacity with increasing blink rate were significant in both age groups. CONCLUSION: The lacrimal drainage capacity increased with increasing blink rate in both younger and older subjects. The lacrimal drainage capacity was significantly lower in the old age group at each blink frequency, indicating that other factors than blink rate are responsible for the lower lacrimal drainage capacity in older age.